Ran the car up and monitored lambda values on MultiECUScan this morning.

Lambda voltage constantly cycles between 70 and 800mV, as per the graph below, with the "Lambda sensor status" constantly cycling through all the available values... Can anyone tell me if this is normal behaviour?

If you look at post #12 in the same thread you will also see another graph showing the sort of signal you should expect to get from a brand new Bosch Lambda sensor.

EDIT: On second looks, your graph is at a different scale to mine on both the X and Y axis but there still seems to be less vigorous activity going on with your airflow signal. Maybe it is worth setting all the same parameters on yours as I used on mine (the same 4 with the same colours) and just running your car up to full engine temperature, then at idle speed only to see if you can get any sort of comparable graph to mine.

1) Run another set of baseline stats, using the four MAF-related parameters you used in your investigation, at tickover with the car warm

2) Remove and clean MAF; then re-run stats

3) Perform ECU/idle actuator reset; then re-run stats

The results were as follows:

Little changed between 1) and 2):

- Average MAF voltage and range were pretty much unchanged - average 1.35V; range 1.23V - 1.45V- Desired air quantity was running higher than actual air quantity - by an average of around 2kg/hr (or 25%) compared with actual air quantity- Over 500 data points recorded in each sample

The discrepancy between desired and actual air quantity led me to perform an ECU/idle actuator reset.

This made quite a difference:

- Desired air quantity was much more closely matched by actual air quantity - average delta reduced to just 0.02kg/hr- MAF output voltage (average and range) was the same as above

On the road, the car drove MUCH better - pulling harder and more smoothly than previously - result!

So, I was about to set off for the MoT retest when I started to get cooling fan errors on the engine ECU...

After a few more investigations, full speed on the fan works OK, but low speed doesn't - and it looks like the resistor in the fan housing has failed (no conductivity at all).

Anyway, I guess this has been the case for a while - so no idea why the engine ECU errors have just started.

Also discovered the fan housing is connected to the radiator by only one of its three screws... hmmm.

Will fix this tomorrow, then head down for a retest first thing Monday - will see how it goes...